Electric wave translation system



July 23, 1929. A, ENSEN 1,722,094

ELECTRIC WAVE TRANSLATION SLS'TEM- Filed Dec. 1924 6. Marisa/7 aw mPatented July 23, 1929.

UNITED STATES OFFICE.

AXEL G. JENSEN 10F RED BANK, NEW JERSEY, ASSIGNOR"TO WESTERN ELECTRICCOMPANY, INCORPORATED, 015 NEW YORK, N. Y., A CORPORATION OF NEW Y ORK.

ELECTRIC WAVE TRANSLATION SYSTEIE.

' Application filed December 4, 1924,. Serial No. 753,813.

This invention relates to electric wave translation systems and moreparticularly to space discharge tube systems wherein the pro-' ductionof undesired oscillations is prevented.

5 It is now well known that, in a space dis charge tube system,oscillations will be generated when the input and output circuits of thetube contain reactances of the proper kind and of the proper value.These oscillations- 0 are generated by virtue of the amplifying actionof the tube, and by virtue of the coupling afforded between thesecircuits by the inherent capacity between the tube electrodes and thetralization may provide a new-path in which parasitic oscillations maybe generated. The

invention to be hereinafter described provides a solution of thisproblem. A

An object of the invention is to prevent the generation of parasiticoscillations in wave translation systems, particularly those includingspace discharge devices.

Another object is to so alter the reactance of wave translation systemsor space discharge tube systems as to avoid a condition favorable to thegeneration of oscillations.

A further object is to prevent the How of oscillatory waves throughspecified paths in a space discharge tube system.

An additional object is to prevent the flow of undesired oscillatorywaves by impeding them.

-A feature of the invention is a space discharge tube systemprovidedwith an impedance element for preventing the flow of oscillatorycurrentsin the system.

Another feature is a space discharge tube system provided with pathsincluding resistance, whereby an oscillatory-condition of the system isavoided.

A further feature is an arrangement of space discharge tubes having theassociated circuits therewith so balanced that the generation ofparasitic oscillations is prevented. v The present invention involvescertaln prlnciples which are applied to systems of space discharge tubesto obtain the objects above enumerated and others. In order to preventundesired oscillations in systems of space discharge tubes, the circuitsincluded therein may be so designed that paths, wherein oscillatorycurrents tend to flow, will contain an element or elements for impedingoscillations. For example, the impedance element may be a resistance. Inanother instance, oscillations may be prevented by providing reactanceelements in certain paths of the system such that no'tendency" foroscillations to buildup will be present. As an example of this, aspace-discharge amplifier may have either its input or output circuit orboth circuits balanced by means of a capacity arranged to neutralize theeffect of interelectrode capacity of thespace discharge tube. Inarrangements ofthis kind, heretofore known, parallel paths between thetube input and output circuits are provided wherein oscillations may begenerated. This invention provides means for preventing oscillations inthese paths by providing, for example, reactance of a particular kind atcertain points therein where reactance of a different kind would berequired to bring about a condition favorablev to the generation ofoscillations. Again, by properly balancing both the input and outputcircuits of a space discharge tube, parasitic oscillations areprevented.

The invention is described in detail in the following specification readin connection.

Fig. 1 represents schematically a space discharge tube system having anoscillation impeding element. r

' having balanced input and output circuits.

Fig. 5 represents anamplifier having an output circuit provided withcapacity reactance for preventing oscillations Fig. 6 represents amodification of the sys tem shown in Fig. 5.

In Fig. 1, a space discharge tube 10 having anode, cathode and controlelectrodes 11, 12 and 13, respectively, is arranged in a circuitincluding an impedance element 14 and a capacity. .element 15 for,preventing oscillations inthe system. The space discharge tube 10 has aninput circuit connected to its con- .trol electrode and cathode whichincludes a resonant circuit 17, comprising a condenser v the anode 11 bya path including condenser 15. The output circuit of tube lO extendsfrom anode 11, through an inductance 24 and a source of space current 23to its cathode. The condenser 25, shown in dotted lines, represents theinherent capacity between the anode 11 and control electrode 13 of tube10 plus the capacity'of the leads connected to these electrodes.

Waves to be amplified may be supplied to the input circuit through thewinding of coil 19 which also represents atransformer, a

wave, collecting conductor-such as a loop antenna, or similar device.Amplified waves may be transmitted toany suitable apparatus external tothe system by suitable coupling means associated with the coil 24-.

In amplifying systems as ordinarily arranged the capacity 25, shown indotted lines, by providing a feed back path from the anode to thecontrol electrode of the tube, permits the transfer of waves from itsoutput circuit to its input circuit which may cause theproduction ofundesired oscillations. In an effort to neutralize the effect ofcapacity 25, the anode 11 is connected to the cathode 12 by a pathincluding the balancing condenser 15. This path is in parallel with thatincluding the capacity 25. Varying currents "flow in the two parallelpaths through the ancing capacity 15 in parallel with thetube respectivehalves ofcoil 1 9 in such manner as to induce electromotive forcestherein which are theoretically equal and opposite, so that no potentialvariations are impressed upon control electrode 13. V 4

In practice, it has been found that the balcapacity 25 constitutes newpaths in which oscillations may be generated, especially, when tubes ofhigh amplifying power are employed, unless additional means is pro-'duced to prevent their occurrence. This fact will be understood when .weconsider that the .-input circuit of tube 10 contains an inductance,representedby the difference between the self-inductance of coil 19 andthe mutual inductance between its two halves, and the output circuitcontains the inductance 24. It is well knownthat a space discharge tubesystem, including inductive reactances in both the input and outputcircuits and capacity coupling between them, will generate oscillationsat certain frequencies for-which these reactances cooperate toconstitute a resonant circuit. I

In order to prevent these reactances inherent in the system fromproducing oscillations the resistance 14 is provided. This by currentstendin to generate oscillations and, by offering a high impedance tothese currents, prevents them from reaching an amplitude such. that thesystem will oscillate.

Resistance 14 may be of such value as not only to prevent oscillationsbut also to cause modulation or demodulation to take place in the inputcircuit. The tube 10 then becomes a modulator or detector as ,the casemay be.

The system of Fig.2 is similar to that of Fig. 1 withthe exception thatresistance 14 is replaced by two resistances 26 and 26connectedrespectively between the cathode of tube 10 and the two outerterminals of the winding of coil 19. These resistances are included inthe parallel paths between the anode and cathode and are of such valueas to greatly impede the flow of oscillatory waves and, if desired, tocause the tube to operate as a distorting device for the impressedWaves, whereby detection or modu-' lation' of. these waves may be,effected. WVhether or not detection or modulation takes place dependsupon the value of the resistresistance is included in the pathtraversed,v

ances which may be varied until they are of a value suitable for thepurpose desired.

In the arrangement shown in this figure the inductance of coil 19 isexcluded from the parallel paths including capacity 25 and resistance 26on the one hand and condenser 15 and resistance 26 on the other. So faras concerns the energy fed back from the output circuit to the inputcircuit, there is no inductive rcactance included in these paths on theinput side of tube 10, hence they are effectively aperiodic. A conditionsuch as to preclude the generation of oscillations therefore exists inthe circuit.

In Fig. 3 the inductance of the coil 19 is also excluded from theparallel oscillatory paths which contain the condenser 27shunted byresistance 29 and condenser 28 shunted by resistance 30 in addition tothe capacity 25 and condenser 15 respectively included in these paths.Since, in the portions of the.

parallel paths on the input side of tube 10, there is included noinductive reactance, oscillations cannot be enerated in these paths.Resistance 29 provid the control electrode andcathode of tube 10 aroundthe condenser 27. A similar resistance 30 is connected in'shunt tocondenser 28 for balancing the resistance 29. By adjusting condensers 27and 28 an accurate balance of the parallel paths may be obtained, andthe input circuit maybe tuned to the frequency of the impressed waves.

es a leak path between .nected to the control electrode.

An additional arrangement for preventing oscillations, comprisingparallel paths between the cathode and anode of a space discharge tube,is illustrated in F ig. 4. Oscillations are prevented in thisarrangement by balancing both the input and the outputcircuits of thetube.

Resonant circuits 17 and 17 are included respectively in the input andoutput circuits of tube 10, and these resonant circuits include as theirinductive elements the coils 19 and 19, respectively. Condenser 15 isarranged to balance the capacity 25 between the anode and controlelectrodes, as already explained. Condensers 15 and 15 provide twoadditional parallel paths complementary to the parallel paths throughcapacities 25 and 15 whereby oscillation currentstending to flow thereinare neutralized. Each of these condensers has a capacity substantiallyequal to the capacity 25 between the anode and control electrode. Sinceboth the input and output circuits of the tube are balanced, it is im-'possible for energy from the output circuit to be supplied to the inputcircuit in such man ner as to establish parasitic oscillations.

In Fig. 5 an amplifier system is illustrated in which only theoutputcircuit is balanced and the inductance of resonant circuit 22 isexcluded from the arallel paths between the anode and control e ectrodeto prevent oscillations,'as was done in the input circuit in.

Fig. 3. Condensers 27 and 28 render the parallel paths between the anodeand cathode of tube 10 in this figure capacitively reactive so far asthe output circuit of the tube is concerned, hence oscillations cannotbe generated in these paths because, as explained above, of the lack ofinductive reactance therein on one side of tubelO. The choke coil 37 isdesigned to have a very large. inductance so that for frequencies atwhich oscillations might otherwise occur the resultant reactance of theoutput circuit is capacitive. In other words the inductance is made solarge that the reactance is substantially pure capacity reactance. Oneterminal of the balancing condenser 15, in this instance, is connectedto the terminal of condenser 28' remote from the cathode, while itsother terminal is con- This condenser functions in the same manner asthe corresponding condensers in the previous figures.

I A second space dischargetube amplifier 35 is here shown with its inputcircuit capacity coupledto the output circuit of tube 10 for obtaining astep-up of voltage of translated waves. a It will be noted that theinput circuit of tube 35 isconnected across both condensers 27' and 36,which are included in series in a. closed loop including. the resonantcircuit 22 and condenser 28', whereas theoutput'circuit of tube 10 isonly connected across-condens-- er 27; y r

"By this arrangement there is provided a. step-up in voltage between theoutput circuit of tube 10 and the input circuit of tube 35. It is thusevident that condenser 27 functions not only as means for preventingsinging in the system, but also as a voltage multiplying means. I I

The amplifier circuit illustrated in Fig. 6 is very similar to thatillustrated in Fig. 5, but.

the input circuit is balanced, and the output circuit is provided withonly capacitive reactance so that an oscillation condition is avoided.

In particular instances the invention has i been found effective whenemployed with tubes having equipotential cathodes, i. e. cathodes heatedby induction or heat radiation such as described in the patent toNicolson 1,459,412 granted June 19, 1923, but this statement should notbe taken to indicate that the utility of the invention is in any mannerlimited to a particular type of tube.

Although, for the purpose of explaining the invention, it has beendescribed in connec-i tion-with certain specific circuit arrangements,the principles involvedare capable of general application to a range ofequivalents not specifically described; but which will readily occur topersons skilled in the art, and consequently this invention is to belimited only as indicated by the scope of the appended claims.

What is claimed is:

1. In a space discharge tube system, a three electrode space dischargetube, input and output circuits for said tube, means for balancing thecapacity between certain electrodes of said tube to prevent oscillationsat frequencies near the frequencies of. the currents impressed on saidinput circuit, and a1 non-reactive impedance cooperating with saidbalancing means to prevent the generation of oscillations in the s stemat frequencies above the frequencies 0 the currents impressed on saidinput circuit. it I 2. In a space discharge tube' system, a threeelectrode space discharge device, a resonant circuit, electrodes of saiddevlce being connected to electrically separate points in said resonantcircuit,'means connected to balance the capacity between two of saidelectrodes to prevent oscillations at frequencies near the said pathscooperating to preventthe production of oscillations having a frequencynear the frequency of the currents impressed on the discharge tube andoscillations having a fre quency above the frequency of the currentsimpressed on the discharge tube,

4. In a circuit including a space discharge tube having an input circuitand an output circuit, means for preventing singing caused by theinternal capacity of the tubes, comprising a capacity connected betweensaid input and output circuits, and means comprising a resistanceincluded in said input circuit in the path of waves tending to establishoscillations for preventing the generation of currents havingfrequencies different from the frequencies of the currents impressed onthe tube.

5. In 'an amplifier, a space discharge tube having three electrodes andcircuits associated therewith for amplifying high frequency waves, saidamplifier including a plurality of paths for waves tending to producesustained 9 oscillations, an impedance in one of'said paths of one kindadapted to prevent oscillations having a frequency near the frequency ofthe currents impressed on the amplifier, and an impedance in another ofsaid paths of a difr 'fcrent kind adapted to prevent oscillations Inwitness whereof, I hereunto subscribe my name this 1st day of December,A. D. 1924.

AXEL G. JENSEN.

